CN113879853A - Feeding device and feeding control method - Google Patents

Abstract

The invention provides a feeding device and a feeding control method, wherein the feeding device comprises a workbench and a mechanical claw, the workbench is provided with a material conveying unit, a material pile is arranged on the material conveying unit, the mechanical claw is arranged in the direction close to a material taking part of the workbench, and the mechanical claw sequentially grabs a single material in the material pile; the material conveying unit comprises a sliding plate and an inclined rod support, the inclined rod support and the material stack are both arranged on the sliding plate, and the material stack is inclined and leans against the inclined rod support; the invention grabs the materials in the material conveying unit step by controlling the movement of the mechanical claw, simply and conveniently realizes the automatic material feeding process, and is beneficial to improving the automation degree of the production line.

Description

Feeding device and feeding control method

Technical Field

The invention relates to the technical field of microwave oven production and manufacturing, in particular to a feeding device and a feeding control method.

Background

Along with the progress of science and technology, more and more manual pipeline operations are changed into full mechanical automation production. In particular to the field of household appliance processing of scale production. How to carry out automatic feeding to the spare part in the household electrical appliances, especially in the microwave oven production manufacturing process, to magnetron fixed bolster, because magnetron fixed bolster size is less, how to realize the automatic feeding process to magnetron fixed bolster, just become the problem that needs the solution in the microwave oven production process.

Disclosure of Invention

In view of this, the present invention is directed to a feeding device and a feeding control method, so as to solve the problem in the prior art that it is difficult to achieve an automatic feeding process of household electrical components, especially an automatic feeding process of a magnetron fixing bracket in a microwave oven production process.

In order to achieve the purpose, the technical scheme of the invention is realized as follows:

a feeding device comprises a workbench and a mechanical claw, wherein the workbench is provided with a material conveying unit, a material pile is arranged on the material conveying unit, the mechanical claw is arranged in the direction close to a material taking part of the workbench, and the mechanical claw sequentially grabs a single material in the material pile; the material conveying unit comprises a sliding plate and an inclined rod support, the inclined rod support and the material stack are both arranged on the sliding plate, and the material stack is inclined and leans against the inclined rod support.

Further, the inclined rod bracket extends upwards in a direction away from the mechanical claw in a toppling mode.

Furthermore, the inclined rod support is inclined towards the opposite direction of the first movement direction and/or inclined towards the opposite direction of the second movement direction.

Further, a protruding block is arranged on the first edge of the material, and the inclined rod support abuts against the protruding block.

Furthermore, a positioning part is arranged on the sliding plate and can be matched with the materials at the lowest layer of the material pile; the positioning part is a single material fixedly connected with the sliding plate, or a positioning lug or a positioning groove arranged on the sliding plate.

Furthermore, at least one side edge of the material is provided with a first folding edge extending upwards, the material is provided with an opening, one side of the opening, which is close to the diagonal support, is provided with a second folding edge extending upwards, the width of the opening is larger than the thickness of the second folding edge, and the length of the opening is larger than the length of the second folding edge.

Further, the workstation includes the material loading mesa, set up a plurality of material conveying units on the material loading mesa, set up the guide way on the material loading mesa, material conveying unit can slide along the guide way.

Furthermore, a sliding groove is formed in the end part of the guide groove, an accommodating part protruding outwards is formed in the edge of the end part of the guide groove, a push plate is arranged on the feeding table top, the push plate is arranged in the accommodating part and extends upwards out of the sliding groove, and the push plate can move along the sliding groove; the workbench comprises a driving device, and the driving device is connected with the push plate and used for driving the push plate to move forwards or backwards.

Further, the workbench comprises a central processing unit for managing and controlling the feeding process; the material taking part of the workbench is provided with a first detection device and a second detection device, the first detection device is used for detecting the maximum height of the material pile, and the second detection device is used for detecting the minimum height of the material pile.

A feeding control method is applied to the feeding device and comprises the following steps:

s1, the central processing unit clears the count value and controls the new material conveying unit to move to the material taking part;

s2, the central processing unit detects the maximum height through the first detection device and judges whether the actual height of the material pile is greater than the maximum height; if yes, return to step S1; otherwise, go to step S3;

s3, the central processing unit detects the minimum height through the second detection device and judges whether the actual height of the material pile is smaller than the minimum height; if yes, return to step S1; otherwise, go to step S4;

s4, the central processing unit controls the mechanical claw to grab the material in the material conveying unit;

s5, the central processing unit detects the minimum height through the second detection device and judges whether the actual height of the material pile is smaller than the minimum height; if yes, return to step S1; if not, the count value is increased by 1, and the step S6 is performed;

s6, the central processing unit judges whether the count value is larger than a preset value; if yes, return to step S1; otherwise, the process returns to step S4.

Compared with the prior art, the feeding device and the feeding control method have the following advantages:

according to the feeding device and the feeding control method, the movement of the mechanical claw is controlled to grab the materials in the material conveying unit one by one, so that the automatic feeding process of the materials is simply and conveniently realized, and the automation degree of a production line is improved; meanwhile, more movable space is reserved for the mechanical claw for the arrangement of the material conveying unit, particularly the inclined arrangement of the inclined rod bracket; in addition, the diagonal bar support is placed in the outer side of the material instead of penetrating through the material, when the gripper grabs the material, the gripper does not need to lift the material to cross the diagonal bar support and then take away the material, the moving path and distance of the gripper are reduced, the grabbing efficiency is improved, and the time is saved.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate an embodiment of the invention and, together with the description, serve to explain the invention and not to limit the invention. In the drawings:

fig. 1 is an isometric view of a loading device according to an embodiment of the invention;

fig. 2 is a top view of a loading device according to an embodiment of the present invention;

FIG. 3 is a side view of a loading device according to an embodiment of the invention;

fig. 4 is an exploded view of a loading device according to an embodiment of the present invention;

fig. 5 is a schematic structural diagram of a material unit and a material stack in the feeding device according to the embodiment of the present invention;

fig. 6 is an exploded schematic view of a material unit and a material stack in a feeding device according to an embodiment of the present invention;

fig. 7 is an exploded schematic view of a material unit and a material stack in a feeding device according to another view angle in the embodiment of the present invention;

fig. 8 is a cross-sectional view of a material unit and a material stack in a feeding device according to an embodiment of the present invention;

fig. 9 is a partial enlarged view of the embodiment of the present invention at a in fig. 8.

Description of reference numerals:

1. a work table; 10. a feeding table-board; 101. a guide groove; 102. a receptacle portion; 103. a chute; 11. a feeding side; 12. a material taking part; 13. a material conveying unit; 131. a sliding plate; 132. a diagonal rod support; 133. a positioning part; 14. a drive device; 141. a cylinder block; 142. an output shaft; 143. pushing the plate; 144. a slider; 145. a guide rail; 15. a first detection device; 16. a second detection device; 2. a gripper; 3. stacking the materials; 31. material preparation; 32. a first folded edge; 33. a first edge; 34. a bump; 35. an opening; 36. a second folded edge; 41. a first direction of motion; 42. a second direction of motion.

Detailed Description

The inventive concepts of the present disclosure will be described hereinafter using terms commonly employed by those skilled in the art to convey the substance of their work to others skilled in the art. These inventive concepts may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.

It should be noted that the embodiments and features of the embodiments may be combined with each other without conflict. The arrows in fig. 2 indicate the direction of movement of the material conveying unit 13.

The present invention will be described in detail below with reference to the embodiments with reference to the attached drawings.

First, it should be noted that the present application (including all the contents of the drawings and the text of the present application) is not limited to the automatic assembly line for microwave oven production and manufacturing, nor to the automatic feeding of the magnetron fixing bracket, nor is the "material" in the present application limited to the magnetron fixing bracket; that is, "material" in this application may refer to an object having a structure similar to or the same as that of material 31 in this application, and on this basis, "automatic feeding" process in this application may also refer to an automatic feeding process of other objects, and "automatic line" in this application may also refer to an automatic line for manufacturing other devices or objects.

For convenience of illustration and understanding, the present embodiment focuses on an automatic assembly line for microwave oven production and manufacturing, and is described as follows:

in order to solve the problem that it is difficult to implement an automatic material loading process in the prior art, the embodiment provides a material loading device, as shown in fig. 1-9, the material loading device includes a workbench 1 and a gripper 2, the workbench 1 is provided with a material conveying unit 13, a material stack 3 is arranged on the material conveying unit 13, the material stack 3 includes at least one material 31, the gripper 2 is arranged in a direction close to a material taking position 12 of the workbench 1, and the single material 31 is sequentially grabbed by movement of the gripper 2; after the gripper 2 grabs the material 31 each time, the material 31 is grabbed and placed in a downstream process for subsequent processing and manufacturing, and then the gripper 2 moves to grab the next time, so that the automatic material feeding process is realized.

Thereby this embodiment snatchs the material 31 in the material conveying unit 13 step by step through the motion of control gripper 2, has realized material automatic feeding's process simply conveniently.

As for the gripper 2, the gripper is a conventional automated gripper, the structure and the operation mechanism of the gripper are the prior art, which are not described herein again, and the structure of the gripper 2 is shown in the drawings in the specification; similarly, the claw of the mechanical claw 2 is matched with the material 31, so that the material 31 can be grabbed; specifically, the jack catch of gripper 2 can be adsorption type, absorbs material 31 through the negative pressure, also can be clamping type, through jack catch centre gripping material 31 etc. in view of the form that the jack catch of gripper 2 snatched the material is prior art, does not describe herein any more. Meanwhile, the quantity of the materials 31 grabbed by the mechanical claw 2 at each time can be 'one grabbed at each time' in the conventional sense, and the quantity of the materials can also be grabbed a plurality of times.

For the workbench 1, the workbench 1 comprises a feeding table top 10, a plurality of material conveying units 13 are arranged on the feeding table top 10, a guide groove 101 is arranged on the feeding table top 10, and the material conveying units 13 are connected with the guide groove 101 in a sliding manner; therefore, after the gripper 2 finishes material taking of one material conveying unit 13, the material conveying unit 13 moves away along the guide groove 101, the other material conveying unit 13 moves to the material taking part 12, and the gripper 2 continues to take materials of the material conveying unit 13 one by one.

The operation of workers is convenient, and the continuous operation of the equipment is convenient; the material conveying unit 13 is provided with a material stack 3, and the material stack 3 is formed by stacking a plurality of materials 31; the guide groove 101 preferably forms a closed circular track, and the material conveying unit 13 can move along the guide groove 101 according to a circular motion track; for the material grabbing process, when the material conveying unit 13 moves to the material taking part 12 of the workbench 1, the mechanical claw 2 grabs the materials 31 on the material conveying unit 13 one by one for many times; for the process of filling the material, when the material conveying unit 13 moves to the loading side 11 of the table 1, the operator needs to place a new material pile on the material conveying unit 13, or adjust or troubleshoot the material conveying unit 13 that is not gripped by the gripper 2.

The end of the guide groove 101 is provided with a sliding groove 103, the end edge of the guide groove 101 is provided with an accommodating part 102 protruding outwards, the feeding table 10 is provided with a push plate 143, the push plate 143 is arranged in the accommodating part 102 and extends upwards out of the sliding groove 103, the push plate 143 can move along the sliding groove 103, and therefore the material conveying unit 13 can be pushed to move in a specific direction in the guide groove 101 by the movement of the push plate 143 along the sliding groove 103. Meanwhile, the accommodating part 102 is provided such that the push plate 143 can be accommodated in the accommodating part 102, and it is possible to prevent the material conveying unit 13 from colliding with the push plate 143 to contact when the material conveying unit 13 moves along the guide groove 101, thereby preventing the material conveying unit 13 from being hindered from moving.

In the process that the pushing plate 143 pushes the material conveying unit 13 to operate, the workbench 1 comprises a driving device 14, the driving device 14 is connected with the pushing plate 143, and the pushing plate 143 can advance or retreat along the chute 103 under the driving of the driving device 14. In the operation process of the single push plate 143, after the push plate 143 in the accommodating portion 102 pushes the material conveying unit 13 to move to the preset position in the guide groove 101 under the driving of the driving device 14, the push plate 143 slides back into the accommodating portion 102 to avoid obstructing the movement of the material conveying unit 13 behind.

Preferably, as shown in fig. 4, the workbench 1 includes a plurality of driving devices 14 and a plurality of pushing plates 143, and the driving devices 14 are matched with the pushing plates 143 in a one-to-one correspondence, the driving devices 14 are disposed below the feeding table 10, the pushing plates 143 penetrate through the feeding table 10 in the vertical direction, and similarly, the sliding grooves 103 also penetrate through the feeding table 10 in the vertical direction.

For the driving device 14, the driving device 14 includes a slide rail assembly and a cylinder assembly, the slide rail assembly and the cylinder assembly are adjacently disposed, the cylinder assembly includes a cylinder body 141 and an output shaft 142, the slide rail assembly includes a slider 144 and a guide rail 145, the cylinder body 141 is connected with one end of the output shaft 142, the other end of the output shaft 142 is connected with a push plate 143, similarly, the push plate 143 is connected with the slider 144, the slider 144 is connected with the guide rail 145, and the slider 144 can slide along the guide rail 145, so that when the cylinder body 141 works, the output shaft 142 can telescopically operate and drive the push plate 143 and the slider 144 to slide along the guide rail 145 together, thereby realizing the forward movement or the backward movement of the push plate 143.

Any one of the material conveying units 13 includes a sliding plate 131, the bottom of the sliding plate 131 is slidably connected to the guide groove 101, the sliding plate 131 is provided with a material stack 3, the sliding plate 131 is provided with an inclined rod bracket 132, the material stack 3 is inclined and leans against the inclined rod bracket 132, that is, the inclined rod bracket 132 supports the material stack 3 formed by stacking a plurality of materials 31; so that the diagonal rod bracket 132 is obliquely arranged, and more movable space is reserved for the mechanical claw 2; in addition, the diagonal rod support 132 is placed outside the material, and the material is not penetrated, so that when the gripper 2 grabs the material, the material does not need to be lifted to cross the diagonal rod support 132 before being taken away, the moving path and distance of the gripper 2 are reduced, the grabbing efficiency is improved, and the time is saved.

One end of the diagonal rod bracket 132 is connected with the sliding plate 131, and the other end of the diagonal rod bracket 132 extends obliquely upwards along the direction away from the gripper 2, so that the diagonal rod bracket 132 tilts towards the direction away from the gripper 2, the distance between the diagonal rod bracket 132 and the gripper 2 is increased, the moving space of the gripper 2 is increased, and the gripper 2 is prevented from interfering with the diagonal rod bracket 132 in the moving process.

Preferably, in fig. 2, before the worker finishes placing the material and before the gripper 2 grips the material, the movement direction of the material conveying unit 13 includes two directions, which are denoted as a first movement direction 41 and a second movement direction 42, the diagonal rod bracket 132 tilts in the direction opposite to the first movement direction 41 and/or tilts in the direction opposite to the second movement direction 42, and this arrangement is such that the diagonal rod bracket 132 generates component forces in the first movement direction 41 and the second movement direction 42, respectively, so that the diagonal rod bracket 132 provides a limiting force to the material stack 3 in both directions, and it is ensured that the corner connecting lines of all the single materials on the material stack 3 are in a straight state rather than a non-aligned curved state, thereby facilitating the precise gripping of the robot arm.

The structure of the material 31 will be described below, wherein the material 31 may be a magnetron fixing bracket or other objects having the following structures; a bump 34 is arranged on the first edge 33 of the material 31, and the inclined rod bracket 132 abuts against the bump 34, so that the material can be limited, and the material stack 3 is prevented from toppling over in the moving process of the material conveying unit 13; in addition, when a worker places materials, the diagonal rod bracket 132 plays a role of guiding, and the materials can slide to the bottom from the upper side along the inclined direction of the diagonal rod bracket 132 without additionally pushing the material stack 3 on the sliding plate 131 to the diagonal rod bracket 132.

The sliding plate 131 is provided with a positioning part 133, and the positioning part 133 can be matched with the material 31 at the lowest layer of the material stack 3, so as to preliminarily position the material 31 at the lowest layer of the material stack 3 and facilitate stacking of the material 31 at the upper layer. The positioning portion 133 may be a single material 31 fixedly connected to the sliding plate 131, or may be a positioning protrusion or a positioning groove provided on the sliding plate 131, wherein the shape and size of the positioning portion 133 are matched with those of the material 31, so as to ensure accurate positioning of the material stack 3, and prevent the material stack 3 from being displaced relative to the sliding plate 131 in the process of moving along with the material conveying unit 13, so as to prevent the material stack 3 from being displaced.

For a single material 31, at least one side edge is provided with a first folding edge 32 extending upwards, the material 31 is provided with an opening 35, the opening 35 is provided with a second folding edge 36 extending upwards at the side close to the diagonal rod bracket 132, the width of the opening 35 is larger than the thickness of the second folding edge 36, and the length of the opening 35 is larger than the length of the second folding edge 36; the arrangement of the first folded edge 32 is convenient for the lower material to limit the upper material, and the arrangement of the opening 35 and the second folded edge 36 enables the opening 35 of the upper material to be sleeved in the second folded edge 36 of the lower material, and the second folded edge 36 of the lower material can quickly position the upper material; in addition, the second folded edge 36 is close to one side of the diagonal rod support 132, so that the inclination direction of the material stack 3 from top to bottom is consistent with the inclination direction of the diagonal rod support 132, and the lug 34 of each piece of material can be always in abutting contact with the diagonal rod support 132.

On the basis of the structure of the feeding device, in order to further improve the automation degree in the feeding process, a first detection device 15 and a second detection device 16 are arranged at a material taking part 12 of the workbench 1, wherein the first detection device 15 is used for detecting the maximum height of a material pile, and the second detection device 16 is used for detecting the minimum height of the material pile; in addition, the workbench 1 comprises a central processing unit for managing and controlling the feeding process; meanwhile, the embodiment provides a material loading control method, which includes:

s1, the central processing unit clears the count value and controls the new material conveying unit 13 to move to the material taking part 12;

in step S1, based on the structure of the feeding device, the guide groove 101 is provided with a plurality of material conveying units 13, and when material taking is not performed for the previous material conveying unit 13 with reference to the moving direction of the material conveying unit 13 on the guide groove 101, the adjacent next material conveying unit 13 is regarded as a new material conveying unit 13; thereby removing the previous material handling unit 13 from the take-out location 12 and moving a new material handling unit 13 to the take-out location 12.

S2, the central processing unit detects the maximum height through the first detection device 15 and judges whether the actual height of the material pile is greater than the maximum height; if yes, return to step S1; otherwise, go to step S3;

preferably, the first detection device 15 is an infrared detector and detects the height of the material stack; specifically, a height limit value of the maximum height is set through an infrared detector, and whether the actual height of the material pile is greater than the maximum height is detected; therefore, under the conditions that the material pile is too much and the material pile is too high, the situation that the mechanical claw 2 cannot reach the corresponding height to cause grabbing failure can be avoided.

S3, the central processing unit detects the minimum height through the second detection device 16 and judges whether the actual height of the material pile is smaller than the minimum height; if yes, return to step S1; otherwise, go to step S4;

preferably, the second detecting device 16 is an infrared detector, and detects the height of the material stack; specifically, a height limit value of a minimum height is set through an infrared detector, and whether the actual height of the material pile is smaller than the minimum height is detected; therefore, under the conditions that the material pile is too few and the material pile is too low, the situation that grabbing fails due to the fact that the mechanical claw 2 cannot reach the corresponding height or the mechanical claw 2 is in space conflict with structures such as the sliding plate 131 can be avoided.

S4, the central processing unit controls the mechanical claw 2 to grab the material 31 in the material conveying unit 13;

after the gripper 2 grabs the material 31, the material 31 is moved and placed in a downstream process, and then the gripper 2 is reset to wait for next grabbing action.

S5, the central processing unit detects the minimum height through the second detection device 16 and judges whether the actual height of the material pile is smaller than the minimum height; if yes, return to step S1; if not, the count value is increased by 1, and the step S6 is performed;

after each grabbing action is executed, the minimum height detection is carried out, so that the feeding process and the action of the mechanical claw 2 can be adjusted effectively and timely according to the actual height condition of the material pile.

S6, the central processing unit judges whether the count value is larger than a preset value; if yes, return to step S1; otherwise, the process returns to step S4.

When the count value is larger than the preset value, the mechanical claw 2 performs a certain number of grabbing actions on one material conveying unit 13, and if the material conveying unit 13 is continuously grabbed, the actual height of the material pile may be smaller than the minimum height at any time; therefore, the arrangement of step S6 makes it possible to stop the successive grasping operations of the individual material transport units 13 in time and then start grasping a new material transport unit 13, and prevents the mechanical gripper 2 from continuing to perform a malfunction due to a failure of an individual component or an error in the above-described individual determination process. Preferably, the preset value is 20.

In addition, in this embodiment, the workbench 1 further includes a base, a housing, an electronic control component, and other structures, which are not repeated herein in view of that the related structures can be purchased or customized from the market and are all the prior art.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.

Claims (10)

1. The feeding device is characterized by comprising a workbench (1) and a mechanical claw (2), wherein the workbench (1) is provided with a material conveying unit (13), the material conveying unit (13) is provided with a material stack (3), the mechanical claw (2) is arranged in the direction close to a material taking part (12) of the workbench (1), and the mechanical claw (2) sequentially grabs a single material (31) in the material stack (3); the material conveying unit (13) comprises a sliding plate (131) and an inclined rod support (132), the inclined rod support (132) and the material stack (3) are both arranged on the sliding plate (131), and the material stack (3) is inclined and leans against the inclined rod support (132).

2. A loading unit according to claim 1, c h a r a c t e r i z e d in that the tilting rod support (132) extends obliquely upwards in a direction away from the gripper (2).

3. A charging device according to claim 2, characterised in that the tilting rod support (132) is tilted against the first direction of movement (41) and/or against the second direction of movement (42).

4. A feeding arrangement according to claim 1, characterised in that the first edge (33) of the material (31) is provided with a projection (34), the diagonal member support (132) abutting against the projection (34).

5. A loading device according to claim 1, characterised in that the sliding plate (131) is provided with a positioning portion (133), the positioning portion (133) being capable of cooperating with the material (31) of the lowermost layer of the stack (3); the positioning part (133) is a single material (31) fixedly connected with the sliding plate (131), or a positioning lug or a positioning groove arranged on the sliding plate (131).

6. A feeding arrangement according to claim 1, c h a r a c t e r i z e d in that the material (31) is provided with a first flange (32) extending upwards on at least one side, that the material (31) is provided with an opening (35), that the opening (35) is provided with a second flange (36) extending upwards on the side adjacent to the sway brace (132), that the width of the opening (35) is larger than the thickness of the second flange (36), and that the length of the opening (35) is larger than the length of the second flange (36).

7. A loading device according to claim 1, characterized in that the working platform (1) comprises a loading platform (10), a plurality of material conveying units (13) are arranged on the loading platform (10), a guide groove (101) is arranged on the loading platform (10), and the material conveying units (13) can slide along the guide groove (101).

8. A feeding device according to claim 7, characterized in that the end of the guide groove (101) is provided with a sliding groove (103), the edge of the end of the guide groove (101) is provided with an accommodating part (102) protruding outwards, the feeding table (10) is provided with a push plate (143), the push plate (143) is arranged in the accommodating part (102) and extends upwards out of the sliding groove (103), and the push plate (143) can move along the sliding groove (103); the workbench (1) comprises a driving device (14), and the driving device (14) is connected with the push plate (143) and used for driving the push plate (143) to advance or retreat.

9. A feeding device according to claim 1, characterized in that said work bench (1) comprises a central processor for managing and controlling the feeding process; the material taking device is characterized in that a first detection device (15) and a second detection device (16) are arranged at a material taking position (12) of the workbench (1), the first detection device (15) is used for detecting the maximum height of a material pile, and the second detection device (16) is used for detecting the minimum height of the material pile.

10. A feeding control method, characterized in that the feeding control method is applied to the feeding device according to any one of claims 1 to 9, and the feeding control method comprises:

s1, the central processing unit clears the count value and controls the new material conveying unit (13) to move to the material taking part (12);

s2, the central processing unit detects the maximum height through the first detection device (15) and judges whether the actual height of the material pile is greater than the maximum height; if yes, return to step S1; otherwise, go to step S3;

s3, the central processing unit detects the minimum height through the second detection device (16) and judges whether the actual height of the material pile is smaller than the minimum height; if yes, return to step S1; otherwise, go to step S4;

s4, the central processing unit controls the mechanical claw (2) to grab the material (31) in the material conveying unit (13);

s5, the central processing unit detects the minimum height through the second detection device (16) and judges whether the actual height of the material pile is smaller than the minimum height; if yes, return to step S1; if not, the count value is increased by 1, and the step S6 is performed;

s6, the central processing unit judges whether the count value is larger than a preset value; if yes, return to step S1; otherwise, the process returns to step S4.

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